After decades of research and development in EUVL (EUV lithography), it appears that EUVL is finally becoming a reality. There were at least fourteen EUV scanners installed worldwide as of the beginning of 2017. The industry consensus seems to be that there is no fundamental technical road block in the implementation of EUVL.
This move towards EUVL has resulted in several competing EUV reticle pattern inspection technologies. One approach is an actinic inspection, which currently has an unacceptable throughput. Two other inspection possibilities include e-beam inspection and DUV inspection. In the DUV inspection approach, a wavelength (typically at 193 nm), which is very different from the EUVL wavelength of 13.5 nm, is used to inspect EUV photomasks. Due to the significant wavelength mismatch, signals from a critical defect on an EUV mask can be very weak. In view of the forgoing, it would be beneficial to find innovative techniques to enhance the defect signals where appropriate.